BRIZENDINE: The thing I have to offer the average psychotherapist is this kind of understanding of hormones and behavior. For example, we used to put females on the analytic couch because they have no libido, right? They were called "frigid"—remember that old word frigid? In my day, frigid women were thought to need psychoanalysis. But what I found when I started testing my patients' testosterone levels was that some women had such low levels that they were almost unmeasurable. When I started giving them back their testosterone, their sex drive came back. And I thought "Oh my God, my entire field has been putting these women on a couch for all these years and saying something's wrong with them." A basic knowledge of the importance of hormones can help therapists recognize when they should start thinking that something biological is going on, so they can encourage their patients to go get that checked out. I think that's a biggie.

RH: How did you first get interested in the role of hormones in brain functioning?

BRIZENDINE: When Prozac came out in 1987, they didn't know that it caused anorgasmia. It wasn't until the early to mid '90s that it became commonly known that all the SSRIs caused ejaculatory delay or anorgasmia. Women were coming and talking to me, their psychiatrist, about it, and I was looking for explanations. I started measuring the hormones of women on SSRIs in the days before the connection was known. I was trying to find the reason why they had great sex function before they started taking meds. This was before we knew the SSRIs caused all these problems.

RH: We can thank Prozac for your body of work?

BRIZENDINE: Prozac gave me my entire career, because of the sexual side effects! I mean, why would a psychiatrist start measuring sex hormones in their patients? That's how I ended up writing The Female Brain. It was written for my patients. It wasn't written for the gender equality studies people in a university's sociology department. And being a feminist myself, I find it odd that the gender police take issue with it. But it is what it is.

Ryan Howes, Ph.D., is a psychologist, writer, musician, and clinical professor at Fuller Graduate School of Psychology in Pasadena, California. He blogs "In Therapy" for Psychology Today. Contact: rhowes@mindspring.com; website: www.ryanhowes.net. Tell us what you think about this article by by logging in and using the comment section below.